The present invention relates to a process for producing fibrous or granular foods, feeds or their materials from a single or combination of two or more natural food materials. The raw materials usable in the present invention include almost all sorts of natural food materials. They include cereals, such as beans, wheat, barley, corn, rice; processed cereals, such as wheat flour, separated protein, degreased soybean meal, and starch; birds and quadruped animals including their meat, skins, bones, milk, blood, eggs and their shells; fish and shells including their skins, bones, organs, shells and eggs; insects and their chrysalis; microorganisms and their protein; skin of oranges; sea weeds; vegetables; seeds and nuts; mushrooms; tea and tobacco leaves; agar-agar and C.M.C.; and additives to food or feed, such as M.S.G., NaCl, and chemical seasonings.
The food or feed (hereinafter called simply "food") and materials produced therefrom by the process of this invention are fibrous or granular in appearance and they may easily be given appropriate elasticity and meat-like texture only by selecting the suitable raw materials. Artificial meat and the like can easily be obtained from a dried food material to restore the original form, and meat-like texture and elasticity by treating the dried food material with cold or hot water. Therefore, these food materials can be used as a substitute for meat to be added to a processed product of meat. The dried materials treated with cold or hot water can be cooked alone or in mixture with ground meat in the same way as ordinary meat.
As will be mentioned later, the process of this invention is quite different in principle from those which utilize the thread spinning technique in producing fibrous artificial meat. The present process is capable of using almost all kinds of raw food as the source material for fibrous or granular food materials (naturally this technique can be applied for making fertilizers, medicines, and various industrial materials); further these raw materials are used without any particular pretreatments, for example, soybeans can be used as is, and a big fish need only to be cut into pieces of an appropriate size before the treatment. Those substances which could not hardly be converted into food, such as seedskin, bone, skin and fin, are successfully converted into food material. Moreover, the raw materials used cannot be ascertained from the appearance of the product. Naturally physical properties of the products are different depending on the nature of raw material, but they should be fibrous or granular in appearance. The fibrous or granular shape is maintained even when they are boiled in hot water or soaked in cold water.
For easy understanding of the present invention, it will be described with reference to fibrous protein which is nowadays actually produced as fibrous food material.
In recent time, many investigations of new vegetable protein foods have been carried out and quite a few protein foods have come into existence. The products are classified into two groups: one is fibrous protein and the other is tissue-like protein. The former is more like natural meat when touched, but it requires more complicated processing, which results in lower nutritional value and lower yield, and hence a higher cost. The latter product, however, has less of the tactile characteristics of natural meat.
The most prevalent method to make fibers from non-fibrous protein is based on spinning said protein in an acid solution using a specified spinning device, but the method is tedious, and the fibers produced are too homogeneous with respect to shape and property to simulate the feel of natural meat. In another method, a high polymer polysaccharide is added to protein and the mixture is treated to give fiber products. However, this method does not afford high quality products.
The present process is a peculiar one, for converting non-fibrous protein into fibers in very simple operations in that it does not require the kind of spinning device which conventional processes do, the manufacturing principle of this process is entirely different from those of conventional ones, and any additive, for example, high molecular compounds and polysaccharides, is not added. The process is much simpler than the conventional methods and the product obtained possesses excellent physical properties which are equivalent or superior to those of other processes.
The method of manufacturing by the present invention will be explained with reference to an example.
When soybean is used as starting material, the whole grains of the soybean are soaked in water to give them an adequate amount of water (the most favorable amount depends on the material and the desired product, in this case 40-55% is desired), and are passed through a very narrow gap between two grindstones which rotate at a high speed (the size of the gap and the speed of rotation depend on both material and desired product, but 0.2 mm or less is favorable when fibrous protein is to be made from soybeans). Then the whole grains of soybean are converted into fibers, and since they contain fat substances, the product serves as a fibrous protein food material.
The conventional method of preparing fibrous protein using the thread-spinning technique requires, in its pretreatment stage, the extraction of pure protein for purification and the complete removal of fat and oil for the purpose of giving the product a meat-like texture. Such a treatment is not necessary at all in the present invention. In addition to whole soybean and degreased soybean, soybean containing fat and oil and degreased soybean to which some oil has been added can also be processed by the present invention into fibers.
In this invention, physical properties of products could be varied extensively by varying the conditions of pretreating the raw material and elements of the apparatus (for example, material, cutting and speed of rotation of two grindstones and the gap between them).
On the other hand, the preparation process of tissue protein by use of an extruder brings about relatively small loss of the raw material and particularly does not require a complicated process, but the treatment which is carried out at a high temperature and pressure necessarily brings about superdenaturation of protein. This results in loss in nutrition, in a non-meatlike texture, and taste. To the contrary, the process of this invention does not involve any special chemical treatment nor any high temperature-high pressure treatment. The whole process goes strikingly fast; the conversion from the raw material to fibrous material requires less than a second. Of course, in the process of our invention, the material being processed momentarily passes a zone of high temperature and pressure during the full course which starts from crushing the raw material and finishes when it has been fiberized or granularized. However, it is too short a time (a few tenths of a second) to cause nutritious defect.
According to the present invention, whole grains of soybean are divided in very tiny pieces in the same manner as they are ground on a mortar. In this case, the protein is particulate and therefore is not oriented. However, when the particles which contain an adequate amount of water travel through a narrow gap (an aperture less than 1 mm, preferably less than 0.5 mm) between two grindstones rotating at a high speed (8-8,000 m/min., preferably 80-600 m/min. by the peripheral speed), they rotate in the same direction, are pressed together under high pressure and are twisted into threads or fibers. Simultaneously, they are heated by the heat evolved as heat of friction, and as a result they are texturized. The water content is the most important factor to make up fibers. If the water is at a very low level, the crushed powder will not be formed into a fiber but will be produced in the form of a fine powder. On the other hand, when the particles contain a high level of water, the crushed powders will disperse themselves in the water and come out as a paste or liquid without adhering to each other. The moisture content necessary to make a fibrous product depends on the nature of raw materials, but generally speaking a water content of 10-65%, and preferably 20-65%, by weight is desired.
In particular, when the raw material contains a high content of protein, evolution of heat of friction is very important to denature the material. The temperature at which denaturation takes place is between 60.degree. and 150.degree. C. for whole grain of soybean. The heat may be applied from outside if necessary, but usually the heat of friction occurs by the frictional rotation of grindstones. However, when the rotation occurs for a short period of time, the material may better be heated intentionally.
Soybeans, being taken as an example, are crushed into tiny pieces together with their skins and cell membranes containing fibrous matters and fat and oil. These tiny fibers and fat are mixed with the protein. In conventional processes these matters should be removed, while in the present invention they need not be removed and moreover the presence of these fibrous matters and fat and oil results in bringing about better texture and taste as well. Fibrous protein of the same level of properties could naturally be produced from high protein materials such as separated protein powder and powdery egg whites (which may contain fat and oil).
Raw materials to be used in this invention include not only cereals and beans which may be used as they are yielded, such as whole soybean, barley, wheat, corn, rice and peanut, but also secondary processed materials such as degreased soybean, wheat gluten, separated protein, soybean curd (or tofu in Japanese). Other materials for use in this invention include almost all food materials covering meat of animals, birds and fishes, and vegetables, sea weeds, and many others. These materials may be used either alone or in admixture of two or more.